Lester Dent (October 12, 1904 – March 11, 1959) was a prolific pulp fiction author, best known as the creator and main author of the series of novels about the superhuman scientist and adventurer, Doc Savage. The 159 novels written over 16 years were credited to the house name Kenneth Robeson. (Wiki)

Synopsis:
High above the skyscrapers of New York, Doc Savage engages in deadly combat with the red-fingered survivors of an ancient lost civilization. Then, with his amazing crew, he journeys to the mysterious "lost valley" to search for a fabulous treasure and to destroy the mysterious Red Death.

Note:
This edition does not include any artwork or illustrations from published works.

I found an earlier posting about Doc Savage by Ralph Sir Edward back in 2009 that answers the question of copyright I think.http://www.mobileread.com/forums/showthread.php?t=62270
Edit: just noticed it's been updated of late. lol. It's hard to know with how Conde Nast is always claiming to own everything no matter what it is. Especially in Old Time Radio programs.